As a technology, integrated photonics has made steady progress since its inception approximately 30 years ago. Optical fiber technology propagates light through glass fibers, wherein the glass fibers are created by drawing molten glass rods down to 10s to 100s of micrometers (μm's) in diameter. With integrated photonics, waveguides are fabricated on semiconductor substrates, wherein the waveguides are typically formed utilizing semiconductor materials, or at least materials compatible with semiconductor manufacturing. For some direct bandgap material systems such as III-V (gallium arsenide (GaAs), indium phosphide (InP), indium gallium arsenide (InGaAs), aluminum gallium arsenide (AlGaAs), etc.) light can be generated, as well as conducted, in the waveguides. In other material systems having indirect bandgaps (e.g., silicon (Si) and germanium (Ge)) light cannot be generated efficiently, and is typically created externally and coupled into the integrated waveguides. Silicon is technologically important because of the enormous infrastructure around silicon complementary metal-oxide semiconductor (CMOS) technology and the potential for tight integration between electronic and photonic technologies.
In order for either direct bandgap or indirect bandgap integrated photonic chips (integrated circuits (ICs), dies) to communicate with other devices on a network, it is necessary to couple from an optical fiber onto the integrated photonics chip, and/or from the photonics chip into the optical fiber. This coupling is dependent on an ability to accurately align the integrated waveguide included in the chip to the high index core of the optical fiber which carries the optical signal. The alignment process is complicated by the dimensions of the waveguides. While the core (e.g., diameter) of the optical fiber can be on the order of 10 microns (μm) or smaller, contained inside a cladding (e.g., of approximately 125 μm), the integrated waveguides can be significantly smaller (100s of nm) due to their high index of refraction. Accordingly, misalignment of an optical fiber/waveguide pair can result in (often appreciable) insertion loss.